RYA Yachtmaster Advanced Navigation 2 — Questions and Answers
Question 1: What is a 'running fix' and when is it used?
- A position fix obtained by taking a bearing of a single object, advancing the position line along the vessel's track, then taking a second bearing of the same or another object (Correct answer)
- A fix obtained while under engine power
- A position obtained by running through shoal water
- A GPS fix taken while the vessel is moving
Correct answer: A position fix obtained by taking a bearing of a single object, advancing the position line along the vessel's track, then taking a second bearing of the same or another object
A running fix is used when only one object is visible. The first bearing is taken and the position line advanced (transferred) along the track made good. When a second bearing is taken, the intersection of the advanced line and new line gives a fix.
Question 2: A depth sounding taken with an echo sounder shows 18.5 m. The tide height is 2.3 m. What is the charted depth at that position?
- 16.2 m (Correct answer)
- 20.8 m
- 18.5 m
- 15.9 m
Correct answer: 16.2 m
Charted depth = sounding − tide height = 18.5 − 2.3 = 16.2 m. Subtracting the tide height removes the tidal contribution and gives the depth referenced to chart datum.
Question 3: When planning a cross-Channel passage from the UK to France, which publication gives standard port tidal predictions for English Channel ports?
- Admiralty Tide Tables, Volume 1 (NP201) (Correct answer)
- UKHO Chart 5011 only
- Almanac only — Admiralty tables are unnecessary
- GMDSS handbook
Correct answer: Admiralty Tide Tables, Volume 1 (NP201)
Admiralty Tide Tables NP201 (European Waters) provides full tidal predictions for standard ports and differences for secondary ports around the English Channel and Western European coasts.
Question 4: A vessel is approaching a headland with a tidal race. How should the skipper time the passage?
- Arrive at or near slack water or when the stream is fair, before it builds to maximum rate (Correct answer)
- Arrive at maximum spring rate for fastest passage
- Arrive at low water for greatest depths
- Any timing is acceptable in a modern yacht
Correct answer: Arrive at or near slack water or when the stream is fair, before it builds to maximum rate
Tidal races can produce dangerous overfalls, breaking seas, and confused water. Passage at slack water or during a fair (favourable) stream before it builds is standard practice. Maximum spring rates in a race can be lethal.
Question 5: What is a 'Secondary port difference' in tide tables and how is it applied?
- A time and height correction listed in tables that, when applied to a standard port's prediction, gives the secondary port's tide (Correct answer)
- A tidal level unique to non-commercial ports
- A correction applied only at spring tides
- A chart correction for non-standard datum
Correct answer: A time and height correction listed in tables that, when applied to a standard port's prediction, gives the secondary port's tide
Secondary port differences include time differences (HW and LW) and height differences (HW and LW heights). These are applied to the standard port predictions after interpolating for the appropriate date.
Question 6: A cross-track error of 0.3 nm is acceptable on an open ocean crossing but not in a narrow channel. Why?
- In a channel, margins are small and 0.3 nm of error could put the vessel on a bank or reef — accuracy requirements scale with the density of hazards (Correct answer)
- Narrow channels have stronger tides that increase error
- GPS is less accurate in channels
- The Yachtmaster standard requires zero error at all times
Correct answer: In a channel, margins are small and 0.3 nm of error could put the vessel on a bank or reef — accuracy requirements scale with the density of hazards
Navigation precision requirements increase as the proximity and density of hazards increases. Offshore, 0.3 nm is negligible; in a 0.5 nm wide channel with shoals either side, it is unacceptable.
RYA Yachtmaster Advanced Navigation 2
What is a 'running fix' and when is it used?